HTTP handler issues

Set the preference

user_pref("network.protocol-handler.app.http", "/usr/bin/firefox");

and point it at the launcher for Firefox on your distribution.

In addition, so Thunderbird can redirect some additional protocls (FTP and HTTPS) add the following

user_pref("network.protocol-handler.app.https", "/location/to/firefox"); user_pref("network.protocol-handler.app.ftp", "/location/to/firefox");

As well as that, you can define another FTP program to handle the FTP transactions (though Mozilla handles them just fine, try the following

user_pref("network.protocol-handler.app.ftp", "/location/to/ftpprogram");